Best friends ex

Recently I found out one of my best friends was dating my other best friends ex. Her ex and her don’t go to my school and the girl who does go to my school only ever met once. I found out because a friend didn’t know that I didn’t know and then I told the girl who dated the guy and then they got mad at me because I TOLD HER. Apparently “it wasn’t my place” but you can’t date a friends ex, that’s the rules of feminism! I knew that they weren’t going to say anything about it to her. So tonight someone who I know and she is best friends with said I was giving her shit about dating this guy. It really isn’t his business and I feel as if I did the wrong thing and I should’ve just kept my mouth shut. Are there people who agree with me or people who agree with my other “friends”